Winemakers often see fining agents solely as clarifiers. There is also a prevailing view that they are a substitute for natural (gravity controlled) clarification. Rather, fining agents should be seen as modifiers of a range of wine attributes. Their appropriate use is a skill and an art form, which requires an understanding of the processes involved and the outcomes desired. Additionally, a single fining agent can affect a number of wine attributes simultaneously. For example, a fining agent might be used to reduce bitterness but might reduce colour at the same time.

Fining, when conducted judiciously, can significantly elevate a wine's quality. This article outlines important factors in fining wines appropriately and includes extensive information on individual fining agents.

Mechanisms of Fining

Fining agents may bind with substances either through:

electrical (charge) interaction - the fining agent and the substance(s) to be removed are of opposite charge and coalesce forming larger particles which settle in the wine

bond formation - a chemical bond is formed between the substance(s) to be removed and the fining agent

absorption and adsorption - the substance(s) to be removed are either caught within the structure of the fining agent, or bind onto the surface of the fining agent

Importance of Bench Testing

Different fining agents will act differently on the same wine. Bench testing with wine samples is therefore strongly recommended (even essential) to determine the outcome of the material used and the optimum dosage required without over- or under-fining.

Bench testing specifically involves adding varying amounts of a fining agent to a number of samples of the wine. Samples are usually of at least half bottle size. Following fining, the samples are assessed for organoleptic quality and the preferred fining dosage is scaled up for the main batch. It is important to prepare and mix the up-scaled fining agent dosage to be used on the bulk wine in the same way that the bench test fining agent was prepared and mixed, otherwise the fining of the bulk batch may produce a different result than the bench testing. The preparation and mixing techniques, and the fining temperature in the up-scaled (bulk batch) case, should all be the same as those used in the bench testing case.

Given the small batches that some winemakers work with, guideline dosages are provided in this article.

Importance of Mixing

Ensuring that the added fining agent(s) are thoroughly mixed throughout the wine is vitally important. This can be achieved by constant stirring and slow addition. For larger batches where mixing in-vessel is difficult, fining is often incorporated into a racking procedure to ensure complete mixing and slow addition. Powdered agents should be re-hydrated (in water) before addition.
It is often noted that it is better not to dilute the fining agent with wine (as opposed to water) before adding to the bulk batch as this will reduce its effectiveness.

Individuality of Each Wine

It is important to remember that every wine is different in terms of its composition, colloidal structure, and the nature of its suspended particles, and therefore every wine will react differently to the same fining.
The effectiveness of a fining agent depends on the agent used, the method of preparation, the method of addition to the wine, the dosage, the wine's pH and metal content, the temperature, the dissolved CO2 level, and any previous treatments the wine has had.

Other Fining Guidelines

The quantity of fining agent used and the contact time between the agent and the wine should both be kept to a minimum. Bench testing can be used to determine the smallest quantity. Fining agents should also be of the highest purity.

Fining Materials List

The following is a relatively exhaustive list of fining agents. These are listed in alphabetical order and include:

Alginate

Alginates, in the form of alginic acid (or algin), are the most widespread polysaccharides (large molecules composed of many linked smaller sugar molecules) used for fining. The acid is extracted from the cell wall of marine brown algae (it is a structural polymer in the cell walls). Alginic acid is a long-chained, high molecular weight polymeric salt (alternating segments of monomers of ß-1,4-D-manuronic acid & L-
guluronic acid, and D-manuronic).

Alginic acids possess a positive electrical charge and are used for general clarification (primarily for removal of yeast cells and tannin complexes). They are usually bound to diatomaceous earth to assist settling.

They are most effective when the pH is below 3.5. Counterfining is often done with gelatine or bentonite.

Blood

Preparation involves mixing in cold water and leaving to swell (dissolution of albumins helped by adding potassium bicarbonate).

Fining with blood is fairly rapid.

Bentonite

Bentonite is a fine montmorillonite clay consisting of aluminium silicate anions (Al2O3.SiO2)(H2O)n neutralised by cations such as sodium, calcium, potassium and magnesium. Bentonite's microscopic structure consists of many plates that position in such a way as to swell considerably when absorbing water.

Bentonite has a negative electrical charge and is used to remove protein (giving "heat stability").

Dosage is usually in the range of 0.2-1.5 g/l.

Bentonite is prepared by making a slurry. It is mixed with warm water and allowed to hydrate for around 24 hours. A 5% weight/volume solution is commonly recommended.

The interaction of bentonite with proteins occurs within minutes.
Bentonite is more effective the lower the pH, and sodium bentonite is the most effective form.

Bentonite creates high quantities of light lees. Bentonite dosages exceeding 0.48 g/l can strip body and flavours and impart an earthy taste to the wine.

Bentonite is often used to counterfine protein fining agents such as gelatine or silica gel.

Sometimes juice is bentonite fined before fermentation for protein removal. It should be noted that this can lower fermentation rate as well as cause stuck ferments and hydrogen sulphide production. Additionally, research has shown that wines settled by enzymes rather than bentonite possess greater aroma/flavour intensity. Protein removal by bentonite post-fermentation is also more effective.

Heat/Protein stability

Protein molecules can polymerise under certain conditions. When these polymer chains become long enough to be visible, a protein haze is seen in the wine. This process is sped up at higher temperatures and is why protein haze is often called "hot instability".

Bentonite can be used to produce heat stable wines (wines that are less likely to form a protein haze) by fining with bentonite. The negatively charged bentonite adsorbs the positively charged protein molecules and the bound protein then settles in the wine.

To test for stability, a sample of wine is heated to 70-80°C (158-176°F) for 6 hours, then cooled to room temperature. This sample is then compared with a control sample. If the treated sample has formed a haze the wine is not stable and requires further fining.

Carbons

Carbons (activated charcoal) work by physical adsorption.

AAA Carbon is used to remove odours (e.g. H2S and mercaptans), is steam-activated, and commonly added at a dosage of around 0.1-1.1 g/l. Sometimes it is used to strip wine for blending, and for ethyl acetate removal at 0.5-2.1 g/l.

KBB Carbon is used to remove colour (e.g. browning & oxidation in white wines). It is acid-activated and commonly used at a dosage of 30-260 mg/l.

These charcoals act through adsorption. They are dirty and hard to handle.
Carbons can provide a means for oxidative deterioration. They are also non-selective in which compounds they strip.

Casein

Casein is the major milk protein, with a positive charge and a molecular weight of approximately 375,000. (1 litre of milk contains about 30 grams of casein and 10-15 grams of albumin.) Casein adsorbs negatively charged particles as it settles.

Casein is most commonly used to decolour white wines, though it does provide aromatic stripping as well. It is usually used in white wines and sherries to improve clarity, as well as being particularly helpful in reducing browning, bitterness (especially when due to excessive skin contact), and oak character. Less clean, older and darker coloured whites benefit greatly from its use.

It is a fairly gentle fining agent and less effective than carbon. However, it does not provide a means for the oxidative deterioration sometimes seen in carbon fined wines. It also reduces the copper content by up to 45% and the iron content by up to 60%.

A typical dosage is 10 and 50 mg/l for general clarification, however some find that higher doses (25 g/l) are required for clarification. Potassium caseinate may be used instead (20-120 mg/l), or skim milk (roughly 15-30 ml/l), or powdered skim milk (roughly 530 mg/l). For browning/bitterness correction a higher dosage of 0.5-1 g/l is often used. This precipitates in the acidic wine environment and does not cause over fining. However, excessive dosages (over 120 mg/l pure casein) have been reported to cause milky/cheesy aromas.

Milk casein is difficult to mix due to it's lack of solubility in acidic solutions and should be mixed in water above pH 8. Sodium or potassium caseinate is usually instead which can be dissolved directly in water. Either form is less effective when stirred into wine directly. Casein absorbs the offending material before flocculating and precipitating quickly in the acidic environment of wine. Slow and thorough mixing is important. The advantage of this is that over-fining is not possible. Casein is often introduced to the bottom of the vessel at fining, then shaken. This prevents clots forming on the surface of the wine.
It is advisable to store casein cold.

Pasteurised milk (whole or skim) is sometimes used instead of casein at 0.2% vol/vol (milk to wine).

Chitin

Chitin is derived from the pulverised exoskeletons of micro-crustaceans. It has a strong positive electrical charge. It is often used with Silica gel. Claro-KC is a propriety name.

They are used for the clarification and tannin reduction of red wines (the proteins attract long-chained tannins, slightly reducing astringency) and are not considered suitable for whites. As far as red wine protein fining goes, they are relatively gentle. Because of this, gelatine is a better fining agent to use against harsh tannins.

For fresh egg whites doses range from 1 to 8 egg whites per barrique (225 L). Typical dosage is probably 1-5 egg whites per barrique. Dried egg white powder or frozen egg whites can also be used at 0.1-0.2 g/l, and dried albumin used at 8-15 mg/l.

Free range organic is considered by some to be the best source of egg whites for fining purposes.

Egg whites are usually prepared by adding a small pinch of salt to some warm water (to help dissolve the globulin which is only soluble in the presence of salts). One part egg-white to two parts salt-water is then mixed. The whites are whisked but not beaten (avoiding foam as this fails to mix). The mixture is then added slowly into the wine whilst stirring continuously.

The wine can usually be racked of the fining lees after one or two weeks.

Egg shell

Egg shells are sometimes used for general clarification and/or decolouration in whites. They are prepared by cleaning the shells, then oven drying them and crushing to a powder.

Gelatine

Gelatine is a collagen, the primary structural protein in animal bone and skin from which it is derived. It is positively charged in wine (isoelectric point is pH 4.7) and binds by hydrogen bonding. It exhibits preferential binding for larger molecules (having more phenolic groups and hydrogen bonding sites). Due to the greater amounts of polymeric phenols in older wines, it has a greater affect on colour and tannin reduction in older wines.

Gelatine is a more heavy handed protein fining agent and is particularly suitable for wines with high levels of extract and phenols (both whites and reds).

It is used to improve clarity and to reduce excessive phenolic character (bitterness/tannins). It is also sometimes used to enhance clarity in juice pre-fermentation. Gelatine can cause a change in hue (tawny/brown to ruby in reds).

Common dosages are 20-100 mg/l (clarification of white wine), 30-150 (young reds). Removal of bitterness is often quoted at 30-240 mg/l, and removal of tannins at 70-530 mg/l. Juice fining requires larger doses (480 mg/l for heavy press juice) to reduce astringency and oxidised colour. In such cases, counterfining with silica gel or bentonite is often practised.

Gelatine is available in powder, sheet, or liquid (30-46% concentration) forms. Liquid gelatines, which have a lower molecular weight, have a lower rate of precipitation but provide better clarification and lees compaction. To prepare solid gelatine, the gelatine is slowly stirred into warm (44 C/ 112 F) water (1-2 g/100 ml). Let the mixture stand for a few minutes and then stir until all lumps are dissolved. Add slowly to wine, stirring continuously, while warm. (Do not boil as heat destroys the protein.)

Coagulum is dense and forms relatively quickly (2-3 weeks).
Gelatine has the advantage that it is easy to prepare and provides a fairly uniform standard. Use of a high grade (100 Bloom or higher, 30 millipoises or higher) gelatine allows for higher absorption. Gelatine that is in its solid form and has little colour or odour is recommended. Gelatine should not be stored for long periods of time as it may deteriorate.

In some cases, the quantity of gelatine required for complete clarification can reduce wine astringency to unacceptably low levels. This is particularly common in white wines of low phenolic content. In such cases, tannin can be added to the wine 24 hours before gelatine fining in the same quantity (by weight) as will be used in gelatine fining. However, most winemakers prefer to counterfine with silica dioxide.

Overfining with gelatine can result in heat and biological instability.

Gum arabic

Gum arabic is a natural gum derived from two species of the acacia tree.

It is most often used to remove copper or iron casse and fruit polysaccharide-protein or fruit polysaccharide-peptide (i.e., protective colloids) combined hazes by absorption.
Because elements of these colloids may adhere to other suspended particles such as tannin precipitates, tartrates or colouring matter, gum arabic may be used to prevent such colloidal coagulation and its associated colour loss.
For the same reason, it has been used to delay (by several months) the crystal growth of tartrates.

It also reduces the surface tension of liquids resulting in increased effervescence. It is thus sometimes added to a sparkling wine base during the second alcoholic fermentation in order to increase the mousse and provide increased mouthfeel in the resulting sparkling wine.

It is claimed that gum arabic can increase the perception of sweetness and smooth mouthfeel.

Isinglass

Isinglass is a collagen (protein) derived from the air bladders of fleshy fish such as sturgeon, catfish, and thread fins.

It is used to remove tannin, phenols, colour, and yeast, as well as general clarification of young whites. Sometimes it is added to sparkling wine to aid riddling.

Condensed tannins are primarily responsible for astringency. Isinglass is less aggressive on condensed tannins than gelatine or casein. Therefore isinglass is less aggressive on astringency and body than these fining agents.

Isinglass is usually used at a rate of 10-50 mg/l. Above 30 mg/l is generally a higher-rate dosage. As a riddling aid in Methode Champenoise production the dosage is typically 15-40 mg/l.

Isinglass is available in two forms: prehydrolysed and fibrous (flocced isinglass). The prehydrolysed form hydrates in 20-30 minutes. This is prepared by dissolving in cool (15 C/60 F) water, enough tartaric, malic or citric acid to give a pH of 2.4-3.0 (this requires ~2.15 g/l tartaric acid in water originally at pH 7). It should be allowed to swell for 24 hours to a few days. The mixture becomes a thick, viscous solution which can then be added to wine (any clots formed should be crushed and pushed through a sieve).

It is important to keep the temperature below 16°C (60°F) otherwise isinglass undergoes partial hydrolysis. This results in smaller molecules which act more like gelatine fining in terms of their activity.

Isinglass produces high lees volumes which settle badly and cling to vessel walls. Wine may therefore require two rackings following isinglass fining. Filtering should only be done when the wine is well clear of isinglass as the agent will clog filters.

Isinglass tends to give results brilliant wines, bright fruit and a smooth/round palate. Some consider it superior to casein in terms of rendering a smoother mouthfeel. It is often used to bring out the fruit character in white wines without altering the tannin significantly. It is more active at lower concentrations than gelatine and therefore provides greater clarity for smaller volumes. There is no danger of over-fining and it also requires less tannin to coagulate compared to gelatine. However, it can take some character away from the nose and the floc tends to be voluminous (>2%) and sometimes settles badly (particulates drape the vessel walls).

Pectin destroying enzymes

Pectin is the material that makes jam set. It consists of large polysaccharide molecules with an electric charge that can cause particulates to remain in suspension. It is often responsible for causing hazes in fruit wines. Grape wines rarely suffer this problem.

Pectin destroying enzymes (e.g. Pectinase, Pectolase) are added to wines to break down the pectin and prevent haze. They are best added to the juice before fermentation.

PVPP (polyvinylpolypyrolidone)

Polyclar is a proprietary name for PVPP. Polyclar SB100 (formerly Polyclar AT) settles more rapidly as opposed to Polyclar 10 which has a greater surface area and thus greater adsorption.

PVPP is derived from Nylon 66 through a manufacturing process in which n-vinyl-2-pyrrolidone is polymerised, resulting in the cross linking of homopolymer chains.

PVPP specifically binds with low molecular weight polyphenols such as monomers and dimers (e.g. cathechin and anthocyanin). PVPP is insoluble, therefore phenolic molecules sorb onto the PVPP surface and precipitate. Binding occurs through a PVPP-carbonyl group to phenolic-hydroxyl group bond (PVPP electrical charge does not account for binding).

PVPP is a gentle fining agent that strips aroma much less than other fining agents. It is used for removing colour (brown and pinking in whites), bitterness (reds and whites), and certain off-flavours (e.g. oxidised flavours).

Dosage is typically 100-700 mg/l in whites, whilst reds typically see 100-200 mg/l. PVPP is usually added directly to the wine, or else with water to a 5-10% slurry before mixing.

PVPP is most useful in the early post-fermentation period but is sometimes used on juice. It settles very quickly (within a few days) but may require filtration after use. It is deemed more effective for white wine colour reduction when used in conjunction with carbon. PVPP also helps settle carbon particles.

It is often deemed preferable to PVPP fine wines young due to its ability to strip wine complexity.

Silica suspensions ("sols", or silica gel, e.g. Kieselsol)

Silica gel is a silicon dioxide colloidal suspension. It is prepared from acidified sodium silicate (Na2SiO3.H2O) which forms silicic acid. It is available in both positively and negatively charged forms and works by adsorption.

Kieselsol, baykisol, and klebsol are all commercial silica gel agents usually made up as a 30% by weight suspension of SiO2.

Silica gel is negatively charged used for general clarification and protein stability. It is a pure fining agent, targeting specific binding sites and thus not affecting aroma of flavour.

Dosage is typically in the range 0.1-0.3 ml/l (liquid silica gel).

Reaction and settling is usually complete within 7-10 days.

As silica gel has no impact on aroma/flavour, over-fining is not a risk. Silica gel can also be used to compact bentonite lees.

Sparkolloid (Scott Laboratories)

Sparkolloid is included here because it is such a popular proprietary blend. It is a blend of polysaccharides in a diatomaceous earth carrier. This fining agent was developed by Scott Laboratories. It possesses a strong positive charge.

Sparkolloid is a gentle clarifier used to remove yeast cells and tannin complexes.

The product comes in cold mix (for general clarity without colour stripping in juice) and hot mix (for clarification of wine).

Recommended dosages are 120-240 mg/l for the cold mix and 120-480 mg/l for the hot mix.

Sparkolloid is prepared by making a 2% solution which is simmered for 15 minutes until the clarifier has dissolved and formed a smooth mixture.

Sparkolloid settles quickly (1.5-2 days) and produces fine lees. It is sometimes used after bentonite fining. It is recommended for fining meads.

Yeast

Yeast has a natural protein removal effect. It is also sometimes used, in the dried (and dead) form, to remove copper sulphate, ethyl acetate, browning, oxidation and excess oak. Doses commonly recommended are 240-1000 mg/l. It is important to rack the wine soon after yeast fining in order to avoid reductive aromas.

Factors Influencing Fining

Temperature

Precipitation of combined particulates is faster at lower temperatures. Protein fining is therefore more effective at lower temperatures (except for bentonite). However, some fining agents are less temperature sensitive than others (e.g. isinglass is less temperature sensitive than gelatine).

Presence of CO2

Wines should be low in dissolved CO2 when fined, since dissolved CO2 will tend to keep particulates in solution and inhibit settling.

pH

The strength of the relative charge of suspended particles decreases as the pH of the wine increases. At high pH, organic protein fining agents may possess a positive charge insufficient to bind to the negatively charged particulates, thus potentially increasing the turbidity of the wine. This phenomenon is called "overfining".

Metal Content

A high metal content in the fining slurry can interfere with the fining process. Some winemakers therefore hydrate fining agents in deionised water.

Overfining

Overfining occurs when an excess amount of fining agent remains in a wine. It often causes clarity instability. A simple test used to detect overfining is to add 0.5 g/l of tannin and check clarity after 24 hours. Clarity is then more or less intense in proportion to the amount of overfining.

Cold stabilisation

Fruit Rot

Juices that refuse to clear due to rot are typically dealt with by bentonite (0.2-0.4 g/l), or gelatine (at 0.03-0.05 g/l) counterfined with silica gel (at 3-6 ml for every g/l of gelatine used).

Timing of fining

The same fining agent impacts differently on wine depending on when it is used. This is due to the presence of different particulates throughout the evolution of the wine. A simple example is bentonite fining. In juice it is used more as a clarifying agent, whereas post-fermentation it is used for heat (protein) stability.

Some winemakers fine juice in the belief that it has less detrimental effects in comparison to wine fining. Others believe that post-fermentation fining is necessary to properly remove the offending material. The majority vote is firmly in the latter camp. However, this does ultimately depend on the fining purpose. For example, fining juice to remove excessive phenolics is reasonably common.

Effects of protein fining agents on tannins

Less aggressive protein agents (e.g., casein, egg white, isinglass) tend to absorb long-chained tannins which appear softer. Thus, they tend to reduce astringency.
An aggressive protein agent such as gelatine tends to bind with tannins generally, particularly short-chained tannins which appear harsher or bitter. Thus, it tends to reduce bitterness (general fruit bitterness and new barrel-bitterness).
Protein fining is softer on a young wine than on an older wine.

Fining and Colour Stability

Stable colour is due to the "condensation" or "co-pigmentation" (i.e. the linking of anthocyanin (colour) compounds and tannins) resulting in polymeric colour pigments. Colour loss occurs through oxidation of monomeric colour pigments which have not condensed with polymeric phenols. Monomeric colour pigments are susceptible to oxidation by oxygen and sulphite ions. Thus, the final wine colour is determined by the rate of condensation versus the rate of oxidation.
Protein fining agents (such as gelatine, casein, isinglass) remove polymeric phenols and tannins. 50-70% of colour pigments are in the polymeric form after one year, and higher pH's result in slower polymerisation and hence a less stable colour.
Therefore, it is recommended to fine for tannic bitterness early on (as soon as the wine is relatively clear). This early fining removes astringency (monomeric phenols) without removing polymeric phenols that have the colour pigments in a stable, co-pigmented form.
Use:
Gelatine to aggressively remove shorter chained young tannins/phenols.
Casein for moderate tannin reduction, removing medium length.
Isinglass or egg whites to remove long chained, older polyphenols/tannins, improving mouthfeel/astringency.

Charges of Various Wine Particulates and Fining Agents

Whilst not universally applicable, the principle of particle charge may be applied to the use of many fining agents. Since many fining agents bind through an electromagnetic attraction to wine particulates, knowing the electromagnetic charge of various fining agents and wine particulates can assist a winemaker in selecting the appropriate fining agents to combat particular problems.
The relative electromagnetic charge of various particulates and fining agents in wines are as follows:
+ particulates: proteins
- fining agents: tannin, yeast, bentonite, silica gel

Silica gel, gelatine

Effective and common (excellent for botrytised wines)
Use 20-100 mg/l gelatine after a 0.1-0.5 ml/l silica gel fining. (A good rule sometimes quoted is to use 3-6 ml of 30% w/v silica gel per gram of protein fining.)
This counterfining regime is particularly popular for treating white juices pre-fermentation instead of using bentonite. This procedure helps separate the press fraction and the gelatine assists in reducing phenolics and brown colour. Dosages vary significantly, depending on the fruit but the gelatine dosage is often quite high. A low dose would be around 0.08 g/l. The last press fraction (last 30% of pressing) may receive a high dosage of gelatine at 1 g/l, as opposed to the free run receiving 0.4 g/l.
Settling time is rapid (can be complete within 8 hours), and is usually certainly complete within 24 hours. The lees will become more compact the longer it is left, however after 2-3 days this may cease to be the case.
The reasoning for using the silica gel first is that it binds rapidly (within a day) with excess positively charged proteins, resulting in a neutral bound particle. The remainder of the wine's particulate matter (yeast, tannin, etc) then has a highly negative net charge which the gelatine is highly effective in binding with.
Traditionally, gelatine was added first and the silica gel added last to bind with any excess gelatine thus preventing overfining. However, there is an argument that if this is done then there is the possibility that insufficient silica gel is added to bind with the excess gelatine then the wine may remain protein unstable.
However, not counter fining gelatine may result in the gelatine staying suspended in the wine for an extended period of time. This may especially be in the case of wines low in tannin (i.e. whites and light reds).

Gelatine, tannin

A tradition approach is to counterfine gelatine with an equal quantity of tannin after having mixed in the gelatine. However, this method risks leaving residual tannins in the wine and therefore a gelatine-silica gel regime is preferred.

Bentonite, gelatine

Gelatine is sometimes used to counterfine residual bentonite haze. This is especially useful in compacting bentonite lees.

Bentonite, Silica gel, Gelatine

Bentonite, Isinglass

Kieselsol, chitin

Gelatine, bentonite

This regime is sometimes used instead of the gelatine-silica gel regime.

Silica gel, Chitin

PVPP and casein

Essentially added together, this strategy allows for thorough action on phenolics whilst avoiding overstripping with single casein or PVPP fining.

PVPP and carbon

PVPP is deemed more effective by some for white wine colour reduction when used in conjunction with carbon. PVPP also helps settle the carbon particles.

Alginate, gelatine/bentonite

Tannin/Silica gel, casein

Traditionally, tannin was often added before counter fining with casein (in a 0.5:1 wt/wt ratio). This risks the possibility of tannins remaining, however, so the contemporary procedure is to instead first fine with silica gel, then counter fine with casein.